A case study of a deformation mechanism around a two-entry gate-road system involving probable time-dependent behavior

Book · Wed Nov 01 04:00:00 EST 1995

OSTI ID:124696

Larson, M K; King, M E; Signer, S P ^[1]; Stewart, C L ^[2]; Stevenson, M A ^[3]

---

1. Bureau of Mines, Spokane, WA (United States). Spokane Research Center
2. Cyprus Shoshone Coal Co., Hanna, WY (United States)
3. Ashland Coal Co., Huntington, WV (United States)

The US Bureau of Mines and Cyprus Shoshone Coal Corp. conducted a study of deformation mechanisms around a longwall gate-road system in an underground coal mine. Of particular interest was roof deformation over the headgate entry. The strata above and below the coal seam are very weak, carbonaceous mudstones that have planes of weakness oriented along the bedding. Visual observations of previous gate roads over several years suggested that deformation was time dependent and resulted in creep along joints or crack growth. Instruments were installed at a test site to measure deformation around the entry, stress changes in the pillar, and loads transferred to support systems. Multipoint extensometers, instrumented bolts, instrumented trusses, biaxial stressmeters, borehole pressure cells, and single-point extensometers were installed. Monitoring continued until the longwall face passed the test site by 38.7 m (127 ft.). Results show that fracture zone arched over the entry from both ribs, most bolts and trusses were loaded past their yield point, and the largest change in secondary principal stress was almost horizontal in the pillar. Displacement measurements in the roof showed classic primary creep.

• OSTI ID: 124696
• Report Number(s): CONF-950811--; ISBN 0-930284-56-9
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
COAL MINING
DATA ACQUISITION SYSTEMS
DEFORMATION
EXPERIMENTAL DATA
LONGWALL MINING
MINE ROADWAYS
MONITORING
RECOMMENDATIONS
ROOF BOLTS
SILTSTONES
STRATA CONTROL
STRESS ANALYSIS
SUPPORT PILLARS
SUPPORTS
WYOMING